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Reqirements of Nozzle Shape ISO9300 versus reality

Reqirements of Nozzle Shape ISO9300 versus reality. Dr.-Ing. B. Mickan; PTB Sonic Nozzle Workshop; 2013-09-20; Poitiers. Content. requirements in ISO 9300 for toroidial nozzles (conventional) indirect measures for nozzle geometry for small nozzles

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Reqirements of Nozzle Shape ISO9300 versus reality

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  1. Reqirements of Nozzle ShapeISO9300 versus reality Dr.-Ing. B. Mickan; PTBSonic Nozzle Workshop; 2013-09-20; Poitiers

  2. Content • requirements in ISO 9300 for toroidial nozzles (conventional) • indirect measures for nozzle geometry for small nozzles • procedure of dimensional measurements at PTB (d > 2 mm) • Examples for larger nozzles • relation to cd-values • Conclusions/discussions/proposals

  3. Requirements out of ISO9300 • divergent section: steps, discontinuities, deviation from circularity shall be < 1% dlocal but Ra shall be < 10-4d (7.1.4) • Inlet section: Ra shall be < 1.510-5d (7.1.3 [7.2.2.4]) • Inlet section: curvature of toroid shall be 1.8 < Rc < 2.2 deviation from ideal toroid form always < 10-4d (7.2.2.4)

  4. Indirect measures of geometry for small nozzles RC = G-1(b) [Geropp]; a = H(RC) (Kliegel/Levine, Hall, Oswatitsch)RC … close to curvature at throat but not identical => You can determine b as well as d out of Flow rate measurements at different pressures. Prior information about d:422 nozzles design value or manufacturer spec. 80 nozzles values for d determined at PTB

  5. Indirect measures of geometry for small nozzles Itis not verylikelythatthecurvaturecanbe fullfilledforsmallnozzlesneartothethroat.

  6. Indirect measures of geometry for small nozzles  d -0.4 Red – manufacturer info Blue – PTB measurement

  7. Indirect measures of geometry for small nozzles In averagewehaveagreementbetween dimensional measurementandflowmeasurement !! Red – manufacturer info Blue – PTB measurement

  8. Y X Y Dh 0 Z zE zA zH Measurement procedure of inner shape (PTB) • 8 lines • 200 points each line • one circle with 360 points at throat

  9. Measurement procedure of inner shape (PTB) Approximation with B-Splines

  10. Measurement procedure of inner shape (PTB) ForcD = 0.995 => displacementthicknessis 0.00125d => Whatis a relevant roughness?

  11. Nozzle shapes from real live Nozzle 71996-2013-08 dthroat = 26,0395 mm

  12. Nozzle shapes from real live Nozzle 71988-2013-08 dthroat = 6,5147 mm

  13. Nozzle shapes from real live Nozzle 71986-2013-08 dthroat = 3,2566 mm

  14. Other Nozzle shapes and cD-Value

  15. Conclusions/discussion/proposals • Shape requirements are not very practical • Roughness criteria to sharp for laminar region? • Deviation from toroid form is not so important far away from throat • Curvature at throat is critical in production as well as for cd-behavior • But not as ciritcal as is seems first • Curvature evaluation depends much on measurement and evaluation procedure

  16. Conclusions/discussion/proposals • Is it helpful to define the measurement procedure of dimensional measurement as well as evaluation of it? • Determination of an average RC (physically weighted [Geropp])? • cD as a function of such a RC (0.8 [?] < RC < 5[?]) (e.g. addionally supported by theoretical/numerical knowledge)?

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